Project Summary Diabetic retinopathy (DR) is a critical complication secondary to diabetes and is the number one cause of blindness in adults worldwide. Despite recent advances using pharmacotherapy, a cure for diabetic retinopathy has yet to be realized. Further understanding of the molecular events that cause disease progression will allow for the development of novel therapeutic solutions for this devastating disease. We believe that recent evidence from large clinical trials demonstrating a strong association between lipid abnormalities and DR progression as well as the discovery that pharmacological activation of liver X receptor (LXR?/LXR?) prevents DR in rodent models, offers a potential breakthrough in our search for cure of DR. To achieve this goal, we propose to analyze retinal levels of SIRT1-LXR as well as investigate the impact DR has on the SIRT1-LXR signaling axis. This signaling axis promotes activation of cholesterol metabolism pathways as well as prevents upregulation of pro-inflammatory genes. Besides measuring retinal levels of SIRT1 and LXR, we also propose to measure retinal cholesterol metabolite leves in diabetic human cells as well as in an animal model of diabetes. This proposal allows for the unique opportunity to characterize human donor retinas into distinct stages of DR progression by using a novel imaging stitching software. This innovative imaging tool is readily used in the Busik Laboratory to determine if donor retinas are in the early, non-proliferative stage or are in the late, proliferative stage. Additionally, to ascertain if activation of this pathway is a potential therapy for DR in vivo, we propose to analyze the effect of SIRT1-LXR activation in a diabetic animal model. We hypothesize that activation of the SIRT1-LXR pathway will improve the deleterious effects seen on retinal cholesterol metabolism and alleviate the inflammatory state active in the diabetic milieu. Michigan State University is home to a world class Molecular Metabolism and Disease Core. Thus, we propose to take advantage of this resources to further characterize and analyze retinal cholesterol levels between control, early stages of DR as well as late proliferate DR stages. Additionally, we currently have the tools necessary to activate the SIRT1-LXR pathway in vivo, allowing us to determine if activation of the SIRT1-LXR pathway prevents DR formation.